Which of the following is a client-server program that opens a secure, encrypted command-line shell session from the Internet for remote logon?

The correct answer is C. SSH.

SSH stands for Secure Shell, a client-server program that opens a secure, encrypted command-line

shell session from the Internet for remote logon. SSH allows users to remotely access and execute

commands on a server without exposing their credentials or data to eavesdropping, tampering or

replay attacks. SSH also supports secure file transfer protocols such as SFTP and SCP1.

VPN stands for Virtual Private Network, a technology that creates a secure, encrypted tunnel

between two or more devices over a public network such as the Internet. VPN allows users to access

resources on a remote network as if they were physically connected to it, while protecting their

privacy and identity2.

IPsec stands for Internet Protocol Security, a set of protocols that provides security at the network

layer of the Internet. IPsec supports two modes: transport mode and tunnel mode. Transport mode

encrypts only the payload of each packet, while tunnel mode encrypts the entire packet, including

the header. IPsec can be used to secure VPN connections, as well as other applications that require

data confidentiality, integrity and authentication3.

SFTP stands for Secure File Transfer Protocol, a protocol that uses SSH to securely transfer files

between a client and a server over a network. SFTP provides encryption, authentication and

compression features to ensure the security and reliability of file transfers.

1: SSH (Secure Shell) 2: What is a VPN? How It Works, Types of VPN | Kaspersky 3: IPsec - Wikipedia :

[SFTP - Wikipedia]